Plastic closure with compression molded sealing/barrier liner

ABSTRACT

A plastic closure that comprises a cap having a base with a peripheral skirt defining the cap interior and threads on the skirt for securing the closure to a container. A liner is secured to the interior of the cap, preferably by being compression molded in situ on the base. The liner consists essentially of a multiplicity of alternating layers of a matrix polymer material such as EVA and a barrier material such as EVOH to resist transmission of gas, water vapor and/or flavorants through the liner. The matrix polymer material preferably is preblended with a compatibilizer material such as a maleic anhydride grafted polymer that ties the matrix polymer material to the barrier material.

The present invention is directed to plastic container closures forbeverage, food, juice, pharmaceutical and like applications, and moreparticularly an improved process for providing closures with sealingliners having resistance to transmission of gases, water vapor and/orflavorants (flavor scalping).

Reference is made to concurrently filed application Ser. No. 08/997,871filed Dec. 24, 1997 (Docket 17138) entitled “Plastic Closure withCompression Molded Barrier Liner” and assigned to the assignee hereof.

BACKGROUND AND OBJECTS OF THE INVENTION

It has heretofore been proposed to provide a plastic closure for acontainer that comprises a plastic cap with an interior liner forsealing engagement with the sealing surface of the container. Forexample, U.S. Pat. No. 4,984,703 discloses a plastic closure thatcomprises a cap having a base with a peripheral skirt and threads forsecuring the cap to a container, and a sealing liner compression moldedin situ to the interior of the cap base. The sealing liner comprises ablend of ethylene vinyl acetate (EVA) and a thermoplastic elastomericmaterial such as olefin or styrene-butadiene-styrene. U.S. Pat. No.5,451,360 discloses a method and apparatus for compression molding theliner in situ within the caps.

Although the closures and methods of manufacture disclosed in the notedpatents address problems theretofore extant in the art, furtherimprovements remain desirable. For example, although soft olefincopolymers such as EVA are sufficiently resilient to provide goodsealing against the sealing surface of a container when the closure isfastened to the container, these materials do not provide an acceptablebarrier against transmission of gases such as oxygen and carbon dioxidethat can deleteriously affect the product within the container. It hasheretofore been proposed to employ a barrier material such as ethylenevinyl alcohol (EVOH) as a gas transmission barrier layer. However,materials of this character tend to be expensive and brittle, and arenot well suited to function as a seal. It is therefore a general objectof the present invention to provide a liner for a plastic closure thatcombines the functions of a seal for engagement with the containersealing surface and an improved barrier against gas transmission, flavorabsorption (flavor scalping) and/or water vapor permeation. Another andmore specific object of the present invention is to provide a liner ofthe described character that is of readily moldable and inexpensivecomposition. Yet another object of the invention is to provide a linerthat satisfies the foregoing objectives and is of clear or translucentconstruction to permit reading through the liner of printing on theclosure. A further object of the present invention is to provide amethod of fabricating such a liner, and a plastic closure embodying sucha liner.

SUMMARY OF THE INVENTION

A plastic closure in accordance with one aspect of the present inventioncomprises a plastic cap having a base with a peripheral skirt definingthe interior of the cap and threads or other suitable means on the skirtfor securing the closure to a container. A liner is secured to theinterior of the base. The linear consists essentially of a multiplicityof alternating layers of a matrix polymer and a barrier material toresist transmission of gas through the liner parallel to the plane ofthe liner. The liner in the preferred embodiment of the invention iscompression molded in situ within the cap, and includes at least ninealternating layers of matrix polymer and barrier materials, preferablyat least thirty-three alternating layers, and most preferably onehundred twenty-nine alternating layers.

The “matrix polymer” is a thermoplastic elastomer, a soft olefinpolymer, or a combination thereof. A thermoplastic elastomer is asynthetic polymer having the processability of a thermoplastic materialand the functional performance and properties of a conventionalthermoset rubber. There are six generic classes of thermoplasticelastomer commercially available, including styrenic block, copolymers(SBC), polyolefin blends (TPO), elastomeric alloys, thermoplasticpolyurethanes (TPU), thermoplastic copolyesters and thermoplasticpolyamides. Thermoplastic elastomers are described beginning at page 64in Modern Plastics Encyclopedia Handbook, published by McGraw-Hill,1994, the disclosure of which is incorporated by reference. Examples ofthermoplastic elastomers are styrene block copolymers as manufactured byShell Chemical under the trademark KRATON. These synthetic polymersconsist of three discrete blocks of the linear or A-B-A type: styrene.An elastomeric alloy is ethylene-propylene-diene terpolymer (EPDM).Another elastomeric alloy consists of compounds of EPDM/PP and butylrubber/PP as manufactured by Advanced Elastomer Systems under thetradenames SANTOPRENE and TREFSIN and disclosed in U.S. Pat. Nos.4,130,535, 4,311,628, 4,130,534 and 4,607,074. In general, thermoplasticelastomers are characterized by a Shore A hardness of 45 to 95 and aflexural modulus of 30,000 to 100,000 psi.

Soft olefin polymers are thermoplastic olefins, homopolymers andcopolymers which are flexible, elastic with a Shore A hardness of lessthan about 100. Typical soft olefin polymers are: metallocene madepolyethylene, ethylene-propylene rubbers, ethylene copolymers and blendsthereof, ethylene copolymers such as ethylene vinyl acetate, ethylenemethyl acrylate copolymers and ionomers and combinations thereof.Examples of soft olefin polymers are alpha olefin substitutedpolyethylenes manufactured using single site catalyst technology (thesematerials are known in the art as metellocene made polyethylenes);ethylene vinyl acetate (EVA) such as manufactured by DuPont under thetrademark ELVAX; polypropylene made with single site catalyst technologyknown in the art as metellocene made polypropylenes; syndiotacticpolypropylenes as marketed by Fina Oil and Chemical; ethylene/propylenecopolymers and styrene-ethylene interpolymers as marketed by DowChemical; and ionomers such as DuPont's SURLYN product line.

The matrix polymer is typically compounded with anti-oxidants,lubricants and other stabilizing materials, as known in the art.

A “compatibilizer” is a thermoplastic that ties two other thermoplasticstogether by a reactive (covalent or dipole—dipole) bond or anon-reactive (chain entanglement) means. Examples includes maleicanhydride grafted polymers or ethylene vinyl acetate grafted polymerssuch as Quantum Chemical's PLEXAR (trademark), Mitsui Petrochemical'sADMER (trademark) and DuPont's BYNEL (trademark) product lines, ethylenemethyl acrylate, and ionomers.

A “barrier material” is a thermoplastic material that has a low gasand/or water vapor transmission rate and a high barrier to odorants andessential oils. The following materials have gas transmission rateslower than EVA, which is an industry standard liner material: EVOH(ethylene vinyl alcohol) such as Nippon Goshei's SOARNOL (trademark)product line and Evalca's EVAL (trademark) product line, nylons such asDuPont's SELAR (trademark) PA, EMS's G21 and Mitsubishi Gas' MXD6product lines, British Petroleum's BAREX (trademark) acrylonitrileproduct line, blends of EVOH and amorphous nylon, blends of EVOH and anionomer such as SURLYN (DuPont), and cyclic olefin copolymers such asmarketed by Ticona. Other suitable barrier materials are blends asdisclosed in U.S. Pat. Nos. 4,977,004 and 5,064,716, and nanocompositesof EVOH or nylon and clay as disclosed in U.S. Pat. Nos. 4,472,538 and5,552,469, the disclosures of which are incorporated herein byreference.

It is currently preferred that the liner also include an additive forreducing the coefficient of friction between the liner and the sealingsurface of the container. Friction reducing additives include metalstearates, microcrystalline waxes, polyethylene glycols, fatty acidesters and amides. These are known as “lubricants” in the art. Thepreferred lubricant is a low molecular weight fatty acid amide materialthat blooms to the exposed surface of the polymer material upon coolingfrom the melt state, thereby reducing the coefficient of frictionbetween the liner and the container sealing surface. Examples are:primary amides with the general chemical structure R—CO—NH2, where R isan alkyl group; secondary amides with the general chemical structureR—CO—NH—R′; where R, R′ are alkyl groups; secondary bis-amides with thegeneral chemical structure R—CO—NH—A—NH—CO—R, where R, R′ are alkylgroups and A is an alkylene group; and blends of the above materialssuch as in U.S. Pat. No. 5,306,542. The lubricant preferably comprisesabout 0.5% to 1.5% of the total liner composition by weight, mostpreferably about 0.5% by weight. The lubricant is preferably compoundedinto the matrix polymer material (along with any desired colorants) bythe material manufacturer. The amount of lubricant and/or colorant isnot included in the calculations of compositions in this application.

The barrier material and the matrix polymer in the liner are each in theamount in the range of about 2% to 50% by weight. The barrier materialmost preferably is provided in an amount in the range of about 6% to 35%by weight in the liner, the compatibilizer material preferably is in therange of about 6% to 20% by weight, the balance consisting of the matrixpolymer.

In accordance with a second aspect of the present invention, a method ofmaking a liner for a plastic closure comprises the steps of extruding apellet that consists of a multiplicity of alternating layers of a matrixpolymer and a barrier material that resists gas transmission, andcompression molding the pellet to form a liner disk in which thealternating layers are oriented generally parallel to the plane of thedisk. The layers in the pellet preferably are coextruded from inputs ofbarrier material, matrix polymer and compatibilizer. These materials maybe separately extruded, or the compatibilizer may be mixed with thebarrier material, the matrix polymer or both prior to extrusion. In thepreferred implementation of the invention, the layers in the pellet arecoextruded from a second input consisting of a blend of the matrixpolymer and a compatibilizer material that promotes adhesion between thematerial layers. The step of compression molding the liner preferably iscarried out by compression molding the liner in situ within a closurecap.

Thus, in accordance with a third aspect of the present invention, thereis provided a sealing liner for a plastic closure that comprises a diskthat consists essentially of a multiplicity of alternating layers ofmatrix polymer material and a barrier material that resists transmissionof oxygen and carbon dioxide through the layers. The sealing linerpreferably is compression molded in situ within a plastic closure from acompression mold charge or pellet in which the alternating layers arecoextruded.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objects, features and advantagesthereof, will be best understood from the following description, theappended claims and the accompanying drawings in which:

FIG. 1 is a functional block diagram of a process for fabricatingcompression mold charge pellets in accordance with a presently preferredembodiment of the invention;

FIG. 2 is a schematic diagram that illustrates compression molding of acharge pellet to form a barrier liner in accordance with the preferredembodiment of the invention;

FIG. 3 is a sectioned elevational view on an enlarged scale of a plasticclosure fabricated in accordance with the preferred method of theinvention illustrated in FIGS. 1 and 2;

FIGS. 4A and 4B are schematic diagrams of charged pellets in closurecaps in tests orientations described in the application;

FIG. 5A is a schematic diagram of a closure showing points at whichphotomicrographs (FIGS. 5C-5G) were taken;

FIGS. 5B-5G are photomicrographs of test results obtained inimplementation of the preferred embodiment of the invention;

FIGS. 6 and 7 are views similar to that of FIG. 3 but showing modifiedliner geometries; and

FIG. 8 is a view similar to that of FIG. 1 but showing a modifiedprocess.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a system 10 in accordance with one presentlypreferred implementation of the invention as comprising a pair ofextruders 12, 14 each having an associated mixing hopper 13, 15.Extruders 12, 14 direct extrudate as first and second inputs to a layergeneration device 16. Layer generation device 16 forms the respectiveinputs into discrete generally parallel layers, and feeds the parallellayers to a layer multiplication device 18. The output of layermultiplication device 18 is an extruded rod from which discrete chargepellets 20 may be cut. Pellet 20 has parallel essentially discretealternating layers, each layer consisting of one of the input materialsto layer generator 16 from extruders 12, 14. The number of parallellayers in pellet 20 is a function of the number of stages and theconstruction of each stage in layer multiplication device 18. In onepresently preferred implementation of the invention, layer generationdevice 16 and layer multiplication device 18 are as disclosed in U.S.Pat. Nos. 5,094,793 and 5,628,950, incorporated herein by reference.Other conventional layer generation schemes may be employed.

FIG. 8 illustrates a modified system 10 a in which the barrier polymer,the matrix polymer and the compatibilizer are fed from associatedseparate extruders 12, 14 a, 14 b to a conventional coextrusion device16 a. The resulting pellet 20 d has multiple flat, spiral or coaxiallayers. In a three-input system configuration as in FIG. 8, the layersof compatibilizer will be thin and disposed between each sequentiallayer of barrier material and matrix polymer. Suitable conventionalcoextrusion devices are disclosed, for example, in U.S. Pat. Nos.4,522,775, and in the background discussion of U.S. Pat. No. 5,628,950.The disclosures of these materials are incorporated herein by reference.As another modification to the embodiment of FIG. 1, barrier materialcan be added to the matrix polymer and compatibilizer input to extruder14. For example, the input to extruder 14 may consist of 10% EVOH, 10%compatibilizer and 80% EVA, all by weight. Extruder 12 a is operated ata lower rate so that total composition remains within the rangesdiscussed above. Disposition of some barrier material within thethermoplastic elastomer layers further enhances the barrier propertiesof the material.

For manufacture of plastic closure barrier liners in accordance with thepresently preferred implementation of the invention, the input toextruder 12 or 12 a at hopper 13 preferably consists of one or morebarrier polymers, while the input to extruder 14 at hopper 15 preferablyconsists essentially of one or more matrix polymers (TPE or soft olefin)and a compatibilizer material. The matrix polymer preferably ispreblended with lubricant and any desired colorants. The input materialsare thoroughly mixed and blended in hopper 15. The barrier polymer inputto extruder 12 preferably is one or more high gas barrier plastic resinsselected from the group consisting of EVOH, nylon, acrylonitrilecopolymers such as styrene acrylonitrile and acrylonitrilemethylacrylate, blends of EVOH and amorphous nylon, nanocomposites ofEVOH or nylon and clay, blends of EVOH and an ionomer, acrylonitrile,cyclic olefin copolymers, and blends thereof. The matrix polymer inputto extruder 14 preferably is selected from the group consisting of EVA,ethylene/propylene copolymers, styrene block copolymers, terpolymers,ionomers, thermoplastic rubbers, styrene/ethylene/butadiene/styreneblock copolymers, styrene/ethylene/butadiene/styrene compounds,styrene/butadiene/styrene block copolymers, EPDM, metallocene madelinear low polyethylene, metallocene made syndiotatic polypropylene,synthetic-elastomer alloys, rubbers such as butyl rubbers, styrenecopolymers such as styrene/ethylene and terpolymers such asstyrene/ethylene/butylene, polypropylene/butyl rubber, and blendsthereof. The compatibilizer input to extruder 14 preferably is selectedfrom the group consisting of maleic anhydride grafted polymers, ethylenevinyl acetate grafted polymers, ethylene methyl acrylate, ionomers andblends thereof. As noted above, a lubricant selected from the groupconsisting of fatty acid esters, glycols, waxes, primary amides,secondary amides, secondary bis-amides and blends thereof, preferably ispreblended with the matrix polymer.

The relative percentages of the barrier polymer, the matrix polymer andthe compatibilizer material depend upon the thicknesses of therespective layers formed at stages 16, 18, which in turn depend upon theextrusion flow rates at extruders 12, 14. The blend input to extruder 14and the relative rates of extrusion preferably are such that the barriermaterial and the matrix polymer in the final liner are each in an amountwithin the range of about 2% to 50% by weight. Most preferably, theamount of barrier polymer in the final output 20 preferably is in therange of about 6% to 35% by weight, the compatibilizer materialpreferably is in the range of about 6% to 20% by weight, with thebalance consisting of the matrix polymer. Increase in the percentage ofthe barrier material increases the cost of the resulting liner. Indeed,a key advantage of the present invention lies in the fact that thelayered construction of the liner increases the barrier properties ofthe liner as compared for example with EVA/EVOH blends, so that a lesseramount of barrier material can be employed than would be the case withblended polymer liners. The amount of adhesive/compatibilizer materialis selected to achieve a desirable amount of bonding between the layers,and to tailor the viscosity of the matrix polymer with which thecompatibilizer is blended. It is to be noted in this respect thatblending of the compatibilizer with the matrix polymer prior toextrusion eliminates a third extruder that would otherwise be necessary,and also permits the compatibilizer to be employed for tailoring theviscosity of the matrix polymer. It is considered desirable that theflow rates of the extrudates input to layer generation stage 16 be asclosely matched as possible. Material flow rates are published bymaterial manufactures, and can be employed in selecting suitablematerials. By mixing EVA with a maleic anhydride compatibilizer, theviscosity of the compatibilizer is reduced more closely to match theviscosity of the EVOH. The viscosities of the separate feed streams mustbe adequately matched to provide proper layer formation. As taught inU.S. Pat. No. 5,628,950, the disclosure of which is incorporated hereinby reference, the melt viscosity difference between the materials of thedifferent layers should be no greater than a factor of five to provideproper layer formations.

It will be understood that the relative component percentages will varywith applications, and will depend among other factors upon hardness andtherefore sealability, and desired removal torque. As to hardness, ithas been found that a liner hardness higher than about 94 or 95 Shore(A) is too hard for proper sealing with the container. When employing amatrix polymer that is relatively hard, such as EVA, the upper limit ofthe barrier material may be relatively low. However, when employing amatrix polymer of relatively low hardness, such as polypropylene/butylrubber, the upper limit of the barrier material may be much higher.

FIG. 2 illustrates a charge pellet 20 placed within a prefabricatedplastic closure cap 22 in the female die 24 of a compression mold 26. Amale die section 28 is closed against pellet 20, cap 22 and die 24 so asto compression mold pellet 20 into a liner that is welded or bonded tothe interior surface of the cap base. That is, referring to FIG. 3, thecharge pellet is compression molded in situ against the base 30 of cap22 so as to form a liner 20 a. This may be accomplished by hand, or morepreferably with the machine disclosed in the above-noted U.S. Pat. No.5,451,360. Cap 22 also includes a skirt 32 that extends from theperiphery of base 30, having internal threads 34 for securing cap 22 toa container. Alternatively, pellet 20 may be separately compressionmolded to form liner 20 a, which may then be adhesively secured withincap 22 against base 30. Such an operation requires additional steps andexpense, and is therefore not preferred. As a second alternative, theliner may be formed in the closures as disclosed in U.S. Pat. Nos.3,674,393, 3,702,148, 3,877,497 and 4,518,336. FIG. 6 illustrates analternative liner 20 b having a flat geometry, as opposed to the liner20 a of FIG. 3 having a thickened periphery. FIG. 7 illustrates a liner20 c having a flat periphery and a thickened mid section for holdingadditional barrier material.

Samples have been fabricated and tested in implementation of the presentinvention. In these samples, the matrix polymer was EVA marketed byDuPont under the trademark ELVAC650. The barrier polymer was either EVOHmarketed by Evalca under the trade designator E105B, or nylon marketedby DuPont under the trademark SELAR PA. The compatabilizer was a maleicanhydride grafted polymer marketed by Mitsui Petrochemical under thetrade designation ADMER QF551.

A first series of samples were fabricated from a compression moldedliner film (i.e., not disposed in caps 22). These test samples werefabricated by extruding material at the desired ratio through theextrusion system of FIG. 1 at a melt temperature of 380 to 440° F. Theextrudate possessed 129 layers. The extrudate, still at melttemperature, was sandwiched between two Teflon-coated metal plates, withthe layers either parallel or perpendicular to the planes of the plates.The assembly was then placed in a Carver press and compressed at about450 psi for about 30 seconds to a film thickness of 25 to 30 mils. Shimswere placed between the plates to determine final thickness. Theassembly (plates and compressed film) was then removed from the pressand placed in a room-temperature water bath for 15 seconds. Thecompressed film was then removed from the plates and dried. Oxygenpermeability was measured according to ASTM D3985 at 100% relativehumidity and 75° F.

A first test sample of this first series was a control sample consistingof 100% EVA. A second sample was another control sample consisting of ablend of 25% EVOH, 65% EVA and 10% compatibilizer. A third test sampleconsisted of 10% EVOH, 80% EVA and 10% compatibilizer with the layers inthe film oriented parallel to the plane of the liner film, as shown inFIG. 4A, prior to compression molding. A fourth test sample consisted of10% EVOH, 80% EVA and 10% compatibilizer, this time with the layers inthe film oriented perpendicular to the plane of the film as shown inFIG. 4B. A fifth test sample consisted of 10% nylon, 80% EVA and 10%compatibilizer with film layers oriented as in FIG. 4A, and a sixth testsample consisted of 10% nylon, 80% EVA and 10% compatibilizer with filmlayers oriented as in FIG. 4B. All films were of identical thickness of25 to 30 mils. Table 1 illustrates the test results:

TABLE 1 Oxygen Permeability (cc*mil/d*atm*100 sq. in.) Durometer TestSample at 75° F. and 100% RH (Shore A Scale) (1) 100% EVA Control 790 92(2) 25% EVOH, 10% c, 110 93 65% EVA (Blend) (3) 10% EVOH, 10% c,  16 9480% EVA (FIG. 4A) (4) 10% EVOH, 10% c,  20 94 80% EVA (FIG. 4B) (5) 10%Nylon, 10% c,  25 94 80% EVA (FIG. 4A) (6) 10% Nylon, 10% c,  31 94 80%EVA (FIG. 4B)

It will be noted that all of the test samples 3-6 in accordance with thepresent invention exhibited a marked reduction in oxygen permeability ascompared with both the 100% EVA control sample 1 and the blend controlsample 2. Indeed, as compared with blend sample 2, the test samples inaccordance with the invention exhibited a marked reduction in oxygenpermeability even with markedly less EVOH. This reduction inpermeability at lesser EVOH is due to the layering in the film and thelayer reorientation that takes place in the film during the compressionmolding operation. It will be noted in this respect that, although thetest results for samples 3 and 5 in which the layers in the film wereoriented parallel to the plane of the film as in FIG. 4A were slightlybetter than the test results when the layers were oriented perpendicularto the plane of the film as in FIG. 4B, the difference in results is notmarked. This is believed to be due to the fact that the heat andpressure of the compression molding operation causes flow of the layeredmaterial radially outwardly so as to reconfigure the layeredconstruction of the pellet even when the layers initially areperpendicular to the final film plane. This is also illustrated in FIGS.5A-5G. FIG. 5A is a plan schematic diagram of a cap and linerillustrating five locations at which samples were cut and stained, andphotomicrographs taken (FIGS. 5C-5G). FIG. 5B shows the initial pelletlayer configuration, with layers in the charge pellet orientedessentially perpendicular to the plane of the cap base. The EVOH layershave taken up stain and are dark in FIGS. 5B-5G. FIG. 5B is at 10×magnification, while FIGS. 5C-5G are at 100× magnification. It is alsoto be noted that the hardness of the samples in Table 1 remainssubstantially constant, indicating that all samples are suitable for useas sealing liners.

Second and third sets of test samples were fabricated, this time in theform of liners compression molded into closures. The test materials wereextruded through the system of FIG. 1 at a melt temperature of 440° F.in proportions to yield the desired weight ratios. Pellets 20 (FIG. 2)were manually cut from the extrudate and placed in closure shells 22.With the pellets 20 still at or near melt temperature, the closure andpellet were placed in a compression mold as in FIG. 2, and thecompression tool was activated to compress the pellet. The film layer inall pellets were at the perpendicular orientation of FIG. 4B. Thecompression force was about 800 psi, and was held for about 15 seconds.Each test closure with liner was then threaded onto a PET bottle finishat industry standard application torque (25 to 30 inch-pounds for a 43mm closure). The finish was then cut from the bottle and epoxied onto ametal plate surrounding a hole coupled to a purge tube. The plate withclosure was then placed in a Mocon OXYTRAN oxygen permeability tester.Oxygen outside of the closure was maintained at 1 atm, 75° F. and 100%relative humidity, and nitrogen gas was used to purge the volume withinthe closure to measure oxygen concentration, and therefore oxygenpermeation through the closure. When oxygen permeability reach steadyreach state, the figure was recorded.

A second set of samples consisting of 20% EVOH, 16% compatibilizer and64% EVA were constructed from pellet layer orientations as illustratedin FIG. 4B. These samples, compression molded in situ into polypropylenecaps, after two months of testing, measured an oxygen transmissivity of0.001 cc/day, as compared with a transmissivity of 0.012 cc/day for anidentical cap with a 100% EVA liner. All liners in all tests were ofidentical 0.025 inch thickness and a diameter of 1.509 inches.

A third set of test samples consisted of liners compression molded insitu into 43 mm plastic caps 22. All liners were 0.025 inches thick witha diameter of 1.509 inches. The following table illustrates the testresults:

TABLE 2 Oxygen Transmissivity Sample (cc/day) 1. 100% EVA Liner 0.012 2.34% EVOH, 1% compatibilizer, 0.006     65% EVA (blend) 3. Layered 20%EVOH, 80% EVA/ 0.0015     compatibilizer

It thus can be seen, somewhat surprisingly, that oxygen transmissivitydid not depend in the test samples on pellet layer orientation prior tomolding. In all of the test samples discussed above, the pelletsinitially contained one hundred twenty-nine alternating layers of matrixpolymer (EVA) and barrier polymer (EVOH or nylon), with thecompatibilizer pre-blended with the matrix polymer. Other tests were runwith similar materials containing only nine layers in the extrudedpellet. When the layers in the initial pellet were oriented parallel tothe final plane of the liner—i.e., parallel to the closure base as inFIG. 4A—the oxygen transmissivity was 0.0017 cc/day. When the layerswere initially oriented perpendicular as in FIG. 4B, the oxygentransmissivity under identical test conditions was 0.0029 cc/day. It isbelieved that, as long as there is sufficient number of layers in theextruded pellet and the final liner, the barrier properties of the linerwill be achieved without regard to the orientation of the layers priorto molding.

It is preferable that the multiple layers each be of substantiallyuniform thickness, although this is not critical because of themultiplicity of layers. It is also preferred that each layer be ofuniform composition. It is anticipated that additional layers of othermaterials exhibiting other desired properties may be employed in certainapplications.

There have thus been disclosed a barrier liner, a closure with barrierliner, and a method of manufacturing the same, that fully satisfy theobjectives and aims previously set forth. The liner is readilymanufactured from otherwise conventional materials, and employingotherwise conventional techniques and equipment. The liner providesimproved efficiency, in terms of the quantity of barrier materialemployed versus permeation and transmission of gasses such as oxygen andcarbon dioxide, water vapor, and essential flavor oils (flavorscalping). Specific matrix/barrier combinations have been disclosed.Other combinations are envisioned for different applications, and willsuggest themselves to persons or ordinary skill in the art based uponthe principles and parameters herein discussed.

All U.S. patents and publications noted above are incorporated herein byreference.

What is claimed is:
 1. A plastic closure that comprises: a plastic caphaving a base with a peripheral skirt defining a cap interior and meanson the skirt for securing the closure to a container, and a linercompression molded in situ onto the interior of said base, said linerconsisting essentially of: (1) continuous layers of matrix polymeralternating with continuous layers of barrier polymer material to resisttransmission of gases, water vapor and flavorants through said liner,totaling at least nine alternating layers of matrix polymer and barriermaterial, and (2) a compatibilizer material comprising a thermoplasticresin for tying the matrix polymer to the barrier material by reactivebonds or non-reactive adhesion mechanisms, said compatibilizer materialbeing disposed in said matrix polymer layers or in separate layersbetween said matrix polymer and barrier material layers.
 2. The closureset forth in claim 1 wherein said barrier material is in the range ofabout 6% to 35% by weight in said liner, said compatibilizer material isin the range of about 6% to 20% by weight, the balance consisting ofsaid matrix polymer.
 3. The closure set forth in claim 2 wherein saidmatrix polymer is selected from the group consisting of thermoplasticelastomers, soft olefin polymers, and mixtures thereof.
 4. The closureset forth in claim 3 wherein said matrix polymer is a thermoplasticelastomer having a Shore A hardness of 45 to 95 and a flexural modulusof 30,000 to 100,000 psi.
 5. The closure set forth in claim 3 whereinsaid matrix polymer is a thermoplastic elastomer selected from the groupconsisting of styrene block copolymers and elastomeric alloys.
 6. Theclosure et forth in claim 3 wherein said matrix polymer is an olefinpolymer having a Shore A hardness less than
 100. 7. The closure setforth in claim 6 wherein said olefin polymer is selected from the groupconsisting of metallocene made polyethylene, ethylene-propylene rubbers,ethylene copolymers, and mixtures thereof.
 8. The closure set forth inclaim 2 wherein said barrier is selected from the group consisting ofEVOH, nylon, acrylonitrile copolymers, blends of EVOH and amorphousnylon, nanocomposites of EVOH or nylon and clay, blends of EVOH and anionomer, acrylonitrile, cyclic olefin copolymers, and blends thereof. 9.The closure set forth in claim 2 wherein said compatibilizer material isselected from the group consisting of maleic anhydride grafted polymers,ethylene vinyl acetate grafted polymers, ethylene methyl acrylate,ionomers and blends thereof.
 10. The closure set forth in claim 2wherein said barrier material comprises EVOH or nylon, and said matrixpolymer comprises EVA.
 11. The closure set forth in claim 2 wherein saidmatrix polymer consists essentially of a blend of one or more matrixpolymers and said compatibilizer material.
 12. The closure set forth inclaim 1 wherein said liner consists of at least thirty-three alternatinglayers.
 13. The closure set forth in claim 12 wherein said linerconsists of one hundred twenty-nine alternating layers.
 14. The closureset forth in claim 1 wherein said liner has a Shore A hardness of notmore than
 94. 15. The closure set forth in claim 1 wherein said linercontains lubricant in the amount of about 0.5% to 1.5% by weight. 16.The closure set forth in claim 15 wherein said lubricant is in theamount of about 0.5% by weight.
 17. The closure set forth in claim 15wherein said lubricant is selected from the group consisting of fattyacid amides, fatty acid esters, microcrystalline waxes, polyethyleneglycols, primary amides, secondary amides, secondary-bis amides, andblends thereof.